Patches giving oestrogen through the skin could be an easy and safe alternative to hormone therapies used to treat prostate cancer, according to new research from Imperial College London.
The study found that oestrogen patches, usually used to treat menopause symptoms in women, reduced levels of testosterone in men to a similar extent as the current hormone treatment, LHRHa injections.
Many prostate cancers need the male hormone testosterone to grow. Using drugs to reduce testosterone in advanced stages of the disease can shrink the tumour or slow growth.
In the 1960s this was done by using oestrogen tablets, but this caused heart and blood clotting side effects for some men. Now, LHRHa injections are the main treatment for reducing testosterone but these may also cause serious side effects including hot flushes, osteoporosis, bone fractures and diabetes.
The Imperial researchers collaborated with colleagues at the Medical Research Council Clinical Trials Unit and clinicians at Imperial College Healthcare NHS Trust. The work was funded by Cancer Research UK.
The team compared LHRHa injections to oestrogen patches in 254 men with locally advanced prostate cancer or prostate cancer that had spread, in order to test the benefits and side effects from the patches.
The results showed that patches appeared to suppress testosterone levels to a similar extent as LHRHa injections. After 12 months, the researchers also found that those having the LHRHa treatment had higher blood glucose and cholesterol levels, which can increase the risk of heart disease, compared to men treated with patches. The patches did not cause the same degree of heart and blood clotting problems caused by oestrogen tablets.
The initial trial has now been extended to study the long-term effectiveness and side effects of oestrogen patches in a larger group of 660 men.
Dr Ruth Langley, from the Medical Research Council Clinical Trials Unit, said: "These promising new findings suggest that we might be able to use oestrogen patches or an oestrogen gel to treat prostate cancer without significantly increasing the risk of heart disease and stroke. We think the reason oral oestrogen causes these side effects is because the oestrogen reaches the liver in high concentrations straight from the stomach, whereas if the oestrogen can be absorbed through the skin, the effect on the liver is avoided."
Professor Paul Abel, from Imperial College London and an honorary consultant in urology at Imperial College Healthcare, said: "The next step is to test if the oestrogen patches are as effective at stopping the growth of prostate cancer as the current hormone treatments. We're now testing this in over 600 patients and early results are expected later this year."
Kate Law, director of clinical and population research at Cancer Research UK, said: "More men than ever are surviving prostate cancer thanks to advances in research, but we still urgently need to find more effective treatments and reduce side effects. This trial is an important step towards better and kinder treatments that could bring big benefits to men with prostate cancer in the future."
The paper, Cardiovascular outcomes in patients with locally advanced and metastatic prostate cancer treated with luteinising-hormone-releasing-hormone agonists or transdermal oestrogen: the randomised, phase 2 MRC PATCH trial (PR09), is published in The Lancet Oncology.
